Design of Ultrawideband Coplanar Waveguide-Fed LI-Shape Planar Monopole Antennas

This letter presents an ultrawideband (UWB) coplanar waveguide (CPW)-fed LI-shape planar monopole antenna. The proposed antenna consists of an L-shaped monopole and an I-shaped open stub monopole connected at the end of a CPW feed line. The UWB operation of the proposed antenna originates from three different surface current paths controlled by the structural parameters of monopole antennas. Experimental results show that the optimized lengths of the antenna provide three resonant frequencies and enhance the bandwidth to satisfy the UWB operation of the proposed antenna. The measured results show that the impedance bandwidth of the proposed antenna ranges from 3.0 to 11.0 GHz, 114.3%. The measured radiation patterns are omnidirectional in H-plane and symmetrical in E-plane. The measured gains range from 1.4 dBi to 4.6 dBi against operating frequencies.